The highest‑energy electron in a hydrogen atom is found in the outermost (highest‑n) energy level or shell that the electron occupies, farthest on average from the nucleus. In the normal, unexcited (ground) state of hydrogen, there is only one electron and it is in the first energy level, n=1n=1n=1, so that is both the lowest and only energy electron. When hydrogen is excited (for example, by absorbing energy in a discharge tube or a star), that same electron can be promoted to higher levels n=2,3,4,…n=2,3,4,\dots n=2,3,4,…, and the electron in the largest nnn at that moment has the highest energy and is found furthest from the nucleus on average.